/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.EnumMap;
import java.util.Map;

/**
 * A {@code BiMap} backed by two {@code EnumMap} instances. Null keys and values
 * are not permitted. An {@code EnumBiMap} and its inverse are both
 * serializable.
 * 
 * @author Mike Bostock
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
public final class EnumBiMap<K extends Enum<K>, V extends Enum<V>> extends
        AbstractBiMap<K, V> {
    private transient Class<K> keyType;
    private transient Class<V> valueType;

    /**
     * Returns a new, empty {@code EnumBiMap} using the specified key and value
     * types.
     * 
     * @param keyType
     *            the key type
     * @param valueType
     *            the value type
     */
    public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V> create(
            Class<K> keyType, Class<V> valueType) {
        return new EnumBiMap<K, V>(keyType, valueType);
    }

    /**
     * Returns a new bimap with the same mappings as the specified map. If the
     * specified map is an {@code EnumBiMap}, the new bimap has the same types
     * as the provided map. Otherwise, the specified map must contain at least
     * one mapping, in order to determine the key and value types.
     * 
     * @param map
     *            the map whose mappings are to be placed in this map
     * @throws IllegalArgumentException
     *             if map is not an {@code EnumBiMap} instance and contains no
     *             mappings
     */
    public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V> create(
            Map<K, V> map) {
        EnumBiMap<K, V> bimap = create(inferKeyType(map), inferValueType(map));
        bimap.putAll(map);
        return bimap;
    }

    private EnumBiMap(Class<K> keyType, Class<V> valueType) {
        super(new EnumMap<K, V>(keyType), new EnumMap<V, K>(valueType));
        this.keyType = keyType;
        this.valueType = valueType;
    }

    static <K extends Enum<K>> Class<K> inferKeyType(Map<K, ?> map) {
        if (map instanceof EnumBiMap) {
            return ((EnumBiMap<K, ?>) map).keyType();
        }
        if (map instanceof EnumHashBiMap) {
            return ((EnumHashBiMap<K, ?>) map).keyType();
        }
        checkArgument(!map.isEmpty());
        return map.keySet().iterator().next().getDeclaringClass();
    }

    private static <V extends Enum<V>> Class<V> inferValueType(Map<?, V> map) {
        if (map instanceof EnumBiMap) {
            return ((EnumBiMap<?, V>) map).valueType;
        }
        checkArgument(!map.isEmpty());
        return map.values().iterator().next().getDeclaringClass();
    }

    /** Returns the associated key type. */
    public Class<K> keyType() {
        return keyType;
    }

    /** Returns the associated value type. */
    public Class<V> valueType() {
        return valueType;
    }

    /**
     * @serialData the key class, value class, number of entries, first key,
     *             first value, second key, second value, and so on.
     */
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        stream.writeObject(keyType);
        stream.writeObject(valueType);
        Serialization.writeMap(this, stream);
    }

    @SuppressWarnings("unchecked")
    // reading fields populated by writeObject
    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        stream.defaultReadObject();
        keyType = (Class<K>) stream.readObject();
        valueType = (Class<V>) stream.readObject();
        setDelegates(new EnumMap<K, V>(keyType), new EnumMap<V, K>(valueType));
        Serialization.populateMap(this, stream);
    }

    private static final long serialVersionUID = 0;
}
